Heterotypic tubular connections at the endoplasmic reticulum–Golgi complex interface
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Electron microscopy and cryoimmunocytochemistry were used to characterize tubular connections in the secretory pathway using rat spermatids as model. Our results support the existence of a complex tubular network enriched in the Golgi matrix protein GM130 that transiently joins the cis-Golgi side and the endoplasmic reticulum. These tubules occasionally contain the endoplasmic reticulum resident protein PDI but not COPII complexes or KDEL receptor. At the lateral edges of the stacks tubules were seen to connect cisternae belonging to the same or adjacent stacks. These connections were observed in all cisternae but preferentially on the cis side. Giantin, Gos28 and Rab6 were detected in the tubules; importantly, we reported the presence of cis–trans heterotypic connections between cisternae. On the trans-Golgi side, we occasionally observed tubules highly immunoreactive for Rab6 connecting the stack with the forming acrosome. Together, our results support the existence of transient continuities throughout the secretory pathways.
KeywordsGolgi complex Spermatid Tubule Electron microscopy Cryoimmunocytochemistry
Endoplasmic reticulum–Golgi intermediate compartment
Protein disulfide isomerase
- Trucco A, Polishchuk RS, Martella O, Di Pentima A, Fusella A, Di Giandomenico D, San Pietro E, Beznoussenko GV, Polishchuk EV, Baldassarre M, Buccione R, Geerts WJ, Koster AJ, Burger KN, Mironov AA, Luini A (2004) Secretory traffic triggers the formation of tubular continuities across Golgi sub-compartments. Nat Cell Biol 6:1071–1081PubMedCrossRefGoogle Scholar